1. Field of Invention
The present invention relates to a current sensing apparatus. More particularly, the present invention relates to an integrated current sensing apparatus.
2. Description of Related Art
In recent years, most of current sensing circuits are implemented by using Hall elements. The Hall element with the characteristic that the sensing voltage of which is in proportion to the current of an object to be measured, can therefore be used to estimate the current of an object by the sensing voltage.
FIG. 1 is a circuit diagram of a current sensing apparatus 100 of prior art. The integrated current sensing apparatus 100 includes a power supply circuit, a Hall element U2, an offset adjustment circuit and a gain adjustment circuit. The power supply circuit provides a constant current to the Hall element U2 via a transistor Q1 to control a sensing voltage. The offset adjustment circuit adjusts an offset of the sensing voltage by changing a ratio between a resistance R9 and a resistance R10. After that, the gain adjustment circuit adjusts a gain value of the sensing voltage by changing the ratio between a resistance R8 and a resistance R7, to generate a rated output voltage, such as 0-5 V.
However, in the conventional current sensing circuit, the resistance values of the resistance R8, R9, R10 may be shifted causing by the instability and the unreliability of the cutting process, such that the ratios between the resistances may not be precise enough. In addition, the characteristic of the resistances may be different in varying temperature, and as a result that the ratios between the resistances may be shifted and the accuracy of current sensing may decline.
In view of foregoing, there is an urgent need in the related field to provide a solution.